Ten-year-old Dareese Shelmon wandered over to help Nether and Tefcon put up the mural. The mural's finishing touch is a QR code that directs people to the name of the vacant house's owner.

Christopher ConnellyNPR

The Johnston Square neighborhood of East Baltimore used to be a thriving, working-class community. But that was a long time ago.

"I don't see kids playing games like we used to play, like the girls playing jacks and skipping jump-rope," says Richard Dean, who has lived here his whole life. "To me that is sad."

Most of the once-tidy row houses on the block sit empty; boarded up, cornices cracking, brick walls warped from water damage. Dean says the sense of community he grew up with disappeared as the neighborhood's population dwindled.

Since its peak in 1950, Baltimore has lost a third of its residents, which left a lot of neighborhoods that look like this one.

In some cases, homeowners died and no one claimed their houses. The majority, however, are owned by the city and a host of absentee landlords. There are so many that everyone just calls them "vacants."

"You're talking about five or more decades of really bad housing policy. And I think that's where it all stems from," says Carol Ott, a one-woman anti-blight campaign who runs the website Baltimore Slumlord Watch.

On a typical day, Ott walks around neighborhood blocks in some of Baltimore's most distressed and dilapidated neighborhoods. She takes pictures and catalogs the vacant homes. Then she digs into public records to find out who owns the buildings, and posts that info online.

Ott set up the site five years ago to draw attention to a shopping center that blighted her own neighborhood. She says it was filled with squatters doing drugs, and it smelled terrible. She wanted to shame the building's owner into fixing it up. The building's owner, a local surgeon, called her, angry.

"Listen, just clean up your crap," she recalls telling him. "I don't care about you. But this is in my neighborhood, [your building] is a problem and my neighbors are sick of it. Just fix it."

And he did — fixed it up, found a tenant — problem solved. Ott's one-off public shame campaign worked. But then she started noticing just how many vacant homes she'd never paid any attention to, in her own neighborhood and across the city, and realized that those vacants were affecting the people who lived near them.

Since then she's cataloged several hundred vacants. It's become a full-time job, cataloging buildings and helping residents navigate city services or get the information they need to sue building owners and this summer she launched a second site to teach residents about their rights and landlords about their responsibilities.

"People just want help," Ott says. "They want to feel like they're no longer being ignored. They want to feel like their concerns matter."

An Open Canvas

The city says there are about 16,000 vacants in the city, but Ott believes the number is much higher. Either way, it's a widespread problem for the city.

But for some, it's a canvas.

Back in Johnston Square, later in the day, a pair of street artists in their early 20s scrape lead paint from the wall of another vacant, preparing it for a mural installation. It's part of a larger project that involves 16 murals by a handful of artists going up around Baltimore this summer.

This mural's creator goes by the name Nether. NPR agreed to use his street name because what he does is illegal. The wall he's chosen for his mural is clearly an interior wall. Drywall with flaking paint shows that one room that was upstairs was painted blue. Another wall has pieces of wallpaper still stuck to it, but these are the only signs a row house once filled what is now just a grassy lot.

"You see where somebody used to live, you know, the interior of their house," he says.

Putting up the mural is quick work. Nether and fellow artist Tefcon roll out six large panels and brush on thick layers of wheat paste. At one point a little boy from the neighborhood joins in.

After all the panels go up, a giant face emerges, youthful and innocent. In the foreground, Nether has drawn the wall the mural adorns and a house of cards. It's a metaphor for the neighborhood's fragility.

"It might sound corny but it's like the saying ... 'you only need one card to knock the house down.' "

The mural project was hatched after Nether realized he was posting art on some of the same buildings Ott had cataloged.

The final touch on the mural fuses public art and public shaming.

The mural is finished off with a giant QR code. When you snap a picture with a smartphone it takes you to Ott's Slumlord Watch website to find out who owns the building, and the politicians who represent the neighborhood.

Bernard Cook, who lives in the neighborhood, walked over to check out the mural.

Baltimore has a blight problem. In some places, whole blocks of abandoned vacant buildings sit boarded up in various states of disrepair. Well, some activists in Baltimore are taking a stand against absentee property owners.

NPR's Christopher Connelly met up with some of them.

CHRISTOPHER CONNELLY, BYLINE: The Johnston Square neighborhood of East Baltimore used to be a thriving working-class community, but that was a long time ago. Richard Dean has lived here his whole life.

RICHARD DEAN: I don't see the children, like, playing games like we used to play, like the girls playing jacks and skipping jump rope and things of that nature. And, you know, you can look. You don't see that. And to me, that's sad.

CONNELLY: Most of the once-tidy row houses on the block sit empty, boarded up, cornices cracking, brick walls warped from water damage. Since its peak in 1950, Baltimore's lost a third of its residents, which left a lot of neighborhoods that look like this one. In some cases, the owners died, and no one claimed their homes, but the majority are owned by the city and a host of absentee landlords.

CAROL OTT: You're talking about probably five or more decades of really bad housing policy, and I think that's where it all stems from.

CONNELLY: Carol Ott is a one-woman anti-blight campaign. She runs a website called Baltimore Slumlord Watch. On a typical day, she walks around blocks like this, taking pictures and cataloging the vacant homes. There are so many that everyone just calls them vacants.

OTT: Oh, wow, look at the wall. Do you see that? That house is about to come down.

CONNELLY: Then she digs into public records to find out who owns the buildings and posts that info online. Ott set up the site five years ago to deal with a blighted shopping center in her own neighborhood. The idea was to shame the building's owner into fixing it, and it worked. Now, she does this work full time, cataloging buildings and helping residents navigate city services or get the info they need to sue building owners.

OTT: People just want help. They want to feel like they're no longer being ignored. They want to feel like their concerns matter.

CONNELLY: The city says there are about 16,000 vacants in the city, but Ott believes that number is much higher. Either way, it's a widespread problem for the city. But for some, it's a canvas. Two blocks away, a pair of street artists in their early 20s are prepping the wall of another vacant for a mural installation.

NETHER: You want to start on the middle and go - or you want to start on the left and the right...

UNIDENTIFIED WOMAN: Yeah.

NETHER: ...and go on the other?

CONNELLY: The mural's creator is called Nether. I'm using his street name because what he does is illegal. They roll out the first paper panel of the mural and start brushing on wheat paste. Half of a man's face goes up, 6 feet tall.

NETHER: OK, watch that. Let me get this part.

CONNELLY: Five more panels go up, and the rest of the face emerges - youthful, innocent. In the foreground, an image of the wall the mural adorns and a house of cards, a metaphor for the neighborhood's fragility.

NETHER: It might sound cheesy, but I thought it was cool. It's like house of cards, and like the saying like you only need one card to knock the house down.

CONNELLY: The mural project was hatched after Nether realized he was posting his art on some of the same buildings Carol Ott catalogued. The mural is finished off with a Q.R. code, so when you snap a picture with a smartphone, it takes you to Carol Ott's Slumlord Watch website to find out who owns the building and the politicians who represent the neighborhood. Bernard Cook walked over to check out the mural.

BERNARD COOK: I think it's fine, beautifies the neighborhood. Like he said, make the slumlords try to beautify their homes and everything. Yeah, that's pretty good.

CONNELLY: There will be 16 murals like this one around the city by the end of summer, each by a different artist, fusing public art and public shaming to try to make a difference. Christopher Connelly, NPR News. Transcript provided by NPR, Copyright NPR.